System for the safe handling of pulverized coal

ABSTRACT

A system for the safe handling of pulverized coal, which system includes conventional coal pulverizing and drying equipment, with cyclones and bag filters added, the latter serving to separate the fine coal from the conveying gas (usually air); and explosion suppression and fire suppression systems, both of which latter systems include conventional components. All three of these systems (coal preparation, explosion suppression and fire suppression) are so combined as to effect the grinding of raw coal whereby to dry and collect the pulverized coal in a oxygen containing atmosphere without property loss due to explosion or fire. A number of explosion detectors and associated extinguishers are strategically located throughout the coal preparation system so that when pressures slightly above operating pressure begin to develop, the explosion extinguishers will be actuated not only to suppress the explosion but also simultaneously to shut down the coal preparation system. Similarly, fire detectors and associated extinguishers are also strategically located throughout the system so that when temperatures slightly above process temperature are sensed the extinguishers will immediately act to suppress the fire and simultaneously shut down the coal preparation system. Preferably the fire suppression system will go into actuation prior to the explosion suppression system and when this happens, the explosion suppression system may be shut down manually if the operator decides it will not be needed, whereby to avoid the expense of having to reload the explosion suppression system.

United States Patent Garbee et a1.

[ SYSTEM FOR THE SAFE HANDLING OF PULVERIZED COAL Inventors: Allen K. Garbee, Lebanon, Ohio;

John A. Honaker, Huntington, W. Va.; James R. Sexton, Monroe, Ohio [73] Assignee: Armco Steel Corporation,

Middletown, Ohio [22] Filed: June 17, 1974 21 Appl. No.2 480,013

Primary ExaminerM. Henson Wood, Jr.

Assistant Examiner-Michael Mar Attorney, Agent, or FirmMelville, Strasser, Foster & Hoffman [57] ABSTRACT A system for the safe handling of pulverized coal, which system includes conventional coal pulverizing &

and drying equipment, with cyclones and bag filters added, the latter serving to separate the fine coal from the conveying gas (usually air); and explosion suppression and fire suppression systems, both of which latter systems include conventional components. All three of these systems (coal preparation, explosion suppression and fire suppression) are so combined as to effect the grinding of raw coal whereby to dry and collect the pulverized coal in a oxygen containing atmosphere without property loss due to explosion or fire. A number of explosion detectors and associated extinguishers are strategically located throughout the coal preparation system so that when pressures slightly above operating pressure begin to develop, the explosion extinguishers will be actuated not only to suppress the explosion but also simultaneously to shut down the coal preparation system. Similarly, fire detectors and associated extinguishers are also strategically located throughout the system so that when temperatures slightly above process temperature are sensed the extinguishers will immediately act to suppress the fire and simultaneously shut down the coal preparation system. Preferably the fire suppression system will go into actuation prior to the explosion suppression system and when this happens, the explosion suppression system may be shut down manually if the operator decides it will not be needed, whereby to avoid the expense of having to reload the explosion suppression system.

9 Claims, 1 Drawing Figure U.S. Patent Oct. 14, 1975 3,912,015

FENWAL DETECTOR 1:1 FENWAL EXTINGUISHER 1x CARDOX DETECTOR O CARDOX EXTINGUISHER SYSTEM FOR THE SAFE HANDLING OF PULVERIZED COAL BACKGROUND OF THE INVENTION 1. Field of the Invention The system for the safe handling of pulverized coal may be used as the coal preparation part of a blast furnace coal injection system, or in other arrangements wherein pulverized coal is to be a reactant; it may also be used in a coal gasification system. The system is de signed for use when pulverizing, drying and collecting coal in an oxidizing atmosphere that could support an explosion or a fire. Bag filters may be used in these coal preparation systems and such filters are especially prone to explosions and/or fires because coal can accumulate in the bag filter and spontaneously ignite.

I-Ieretofore, coal pulverizing has been done without the benefit of fire'and explosion protection. Most conventional applications feed the finely divided coal directly to burners or combustion chambers. The conveying air is used as all or part of the air required to burn the coal. In such applications, premature ignition does not cause explosions if the velocity of the conveying air of kept above the flame propagation velocity for pulverized coal. Burning coal particles are simply blown into the combustion chamber. In those applications to which the instant system is directed, however, the burning particles could enter the bag filter or storage vessel and cause an explosion or a fire. The proposed system is designed to prevent such explosions or fires.

2. Description of the Prior Art No search of the prior United States patent art has been made in conjunction with the preparation of this application. The proposedsystem, however, does make use of known explosion prevention arrangements and of known fire prevention arrangments. The explosion detector components and the explosion extinguishers incorporated in the instant system are marketed under the trademark Fenwal by Fenwal Incorporated. The fire detector components and first extinguisher components are marketed under the trademark Cardox by Chemetron Corporation. It is not believed, however, that any of these components have been incorporated in systems for handling coal dust in the manner taught herein. It is true, however, that both the "Fenwal and Cardox systems have been used in a variety of other industrial processes. I

SUMMARY OF THE INVENTION The invention herein lies in combining the known Fenwal components into a single process system for safe operation of a coal grinding and collecting stream; similarly, the known Cardox components may also be incorporated into this system. It is to the strategic locations of the various detectors and extinguishers in 'the coal grinding and collecting stream that the invendown, but also the Fenwal components may not be actuated, depending on the circumstances, thus saving the cost of having to replace the bromochloromethane or the like. If, however, the explosion is the first event to be sensed, the Fenwal extinguishers will, of

course, be actuated whereby to suppress the explosion and shut down the system until such time as proper corrections may be made.

BRIEF DESCRIPTION OF THE DRAWING The drawing consists of a single schematic diagram of a coal preparation system to which the explosion components and fire components have been applied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical coal preparation system to which the instant system for the safe handling of pulverized coal may be applied may be comprised of a raw coal storage bunker 10 having feeder means 11 for directing the raw coal lumps into a pulverizer 12 through a duct 13. Coal feed means 13a may be employed to insure properly controlled feeding of the pulverizer 12. It will be understood that means generally indicated at 14 are provided by means of which hot air is directed into the pulverizer 12. The means 14 may, for example, be comprised of a fan and a direct fired heater. Means not shown but which are well known in the art are provided for the pulverizer 12 and heater 14 to regulate the temperature of the air in the pulverizer in accordance with, among other things, the moisture content of the lump coal going into the pulverizer. Typically such content may be in the neighborhood of 6%. Generally it is desirable to have the coal particles leaving the pulverizer to have a low amount of surface moisture, a content in the neighborhood of one/half percent. It is desirable that the particles leaving the pulverizer have 80% thereof which will pass through 200 mesh grid; this means that the pulverizer coal particles will have a texture similar to common face powder. It is because of the dust-like nature of the pulverized coal, and the presence of an atmosphere that can support combustion, that explosion and fire hazards exist in the system.

The pulverized coal leaves the pulverizer 12 through a coal pipe 15 to a cyclone separator 16. Typically, of the coal powders introduced into the known cyclone separator 16 will be discharged directly into the coal storage tank 17 via the duct 18. The fines, constituting the remaining 10% of the pulverized coal entering the cyclone separator 16, exit via the duct 19 into a pair of bag filters or the like 20 and 21 through the duct extensions 19a and 19b. The fines thus separated and collected in the filters 20 and 21 are discharged into the coal storage tank 17 via the ducts 22 and 23.

The instant invention is the protection of that part of the coal separation system so far described from damage due to either explosion or fire. What happens to the coal after it is collected in the storage tank 17 is not of vital importance to the invention. By way of example, however, such coal may be directed via ducts 24 and 25 to coal tanks 26 and 27 having discharge conduits 28 and 29 directed to the feed means for a blast furnace and the like, not shown. Or it may be that the coal from the storage tank or reservoir 17 may be led therefrom via the conduit 30 to a tank 31 which may be connected to a coal gasification system, not shown. It is also known, by way of further example, to protect that part of the system from tank 17 through tanks 27 and 31 by the use of an inert gas in the general manner taught in U.S. Pat. No. 3,720,351 to Coulter et al.

In the coal pulverizing process accomplished by the apparatus so far described, relatively wet lump coal from the bunker is fed by the means 11 into a coal pulverizer 12 which ia a classifier (not shown) located in the top section of the pulverizer. The ground coal is air-conveyed by conventional means, also not shown, under positive pressure out of the mill 12 through the duct 15 which typically may be a 30" diameter pipe for a distance which typically would be in the neighborhood of approximately 130 into the cyclone 16 for further distribution into the process. As indicated, the outlet side of the cyclone 16 is connected to two bag collectors 20 and 21 which typically may be located approximately 40' from the top portion of the cyclone. (Although a positive pressure system is described herein, it will be understood by those skilled in the art that a negative pressure system could be employed.)

The protection provided by this invention starts with the pulverizer 12 and includes the interconnecting ductwork to the cyclone outlet and the two dust collector hoppers 20 and 21.

The explosion detection portion of this system is comprised of pressure-sensitive explosion detectors that will respond to the pressure wave generated during an incipient explosion. The detector will, in turn, complete a circuit through the power unit to actuate each high-rate discharge extinguisher electrically connected to the power unit. As indicated, the sensing devices and extinguishers are well known as illustrated by the Fenwal devices available in the marketplace. Proper location of these known devices, however, in the coal preparation system is believed novel and of much importance. A detailed description, therefore, of the means interconnecting the detectors and the extinguishers, whether they be of the Fenwal type for suppressing explosions, or of the Cardox type for extinguishing fires, will now be depicted in detail. The operation of these devices is well known to those skilled in the art and is readily available in literature published concerning the Fenwal" and "Cardox" systems. It is noted, however, that these detection devices may be actuated due to their sensitivity to ultra violet changes and temperature changes as well as to pressure differentials.

In applying the Fenwal components to the instant system for the safe handling of pulverized coal, the first explosion detector 32 is located in connection with the outlet duct 15 of the pulverizer 12; in actual practice, this would be approximately I inch from the pulverizer. The second explosion detector 33 is also located on the outlet duct but further up from the mill 12; in actual practice, this duct 33 would be approximately inches from the mill 12.

As an aid in considering this invention, it will be observed that the same symbol is used to represent all of the explosion detectors, a different symbol is used to represent all of the explosion extinguishers; similarly, a still different symbol is employed to represent each of the fire detectors while yet another symbol is used to represent each of the fire extinguishers.

The third explosion detector 34 is located near the top of the air conveyor duct or coal pipe 15 and in practice this would be at a distance of approximately 100 inches from the mill 12. The fourth detector 35 is located on the outlet duct 19 of the cyclone 16. The fifth and sixth detectors 36 and 37 are located on the inlet ducts 19a and 19b to the dust collectors represented by the bag filters generally indicated at 20 and 21. The seventh and eighth explosion detectors 38 and 39 may be located on the dust collectors 20 and 21 at the inlet side thereof above the floor grading and at the base of the filtering box (not shown).

For explosion suppression a number of extinguishers responsive to the explosion detectors are strategically arranged. A first extinguisher 40 is located above the coal pulverizer or mill l2 and releases its agent down the outlet duct 15 and into the pulverizer 12. Typically this would be a l0-liter high-rate discharge extinguisher 40.

a second high-rate discharge extinguisher 41 is located somewhat further from the mill l2 and is oriented so as to release its agent down the duct 15 toward the pulverizer 12. In practice, this may be a 5-liter extinguisher.

Third and fourth explosion extinguisher 42 and 43 are located towards the top end of the coal pipe or air conveyor 15 and are oriented so that both of these extinguishers 42 and 43 direct their agent down the duct 15 towards the pulverizer 12. typically these extinguishers may be of l0-liter capacity.

To protect the cyclone 16, a fifth explosion extinguisher 44 is mounted on its top section behind the outlet duct 19; in practice, this would normally be a 5-liter high-rate discharge extinguisher. This extinguisher 44 releases its agent into the cyclone 16 through a spreader assembly (not shown) which distributes the agent into the cyclonic air. A sixth explosion extinguisher is located on the outlet duct 19 of the cyclone 16 and releases it agent down the duct to the interior portion of the cyclone. In practice this extinguisher 45 may also be of 5-liter capacity.

Seventh and eighth extinguishers 46 and 47 are located on the feed ducts 19a and 19b of each of the two dust collectors 20 and 21. These extinguishers 46 and 47 are mounted on the ducts and release their agent down the ducts 19a and 19b to the dust collectors 20 and 21. Typically these extinguishers 46 and 47 may be of 5-liter capacity. In the hopper of each dust collector 20 and 21, there are located ninth and tenth extinguishers 48 and 49. Each of these extinguishers 48 and 49 is located under the floor grading (not shown) so as to release its agent into its respective hopper through a spreader assembly (also not shown) which will distribute the agent into a cone of In practice, these extinguishers 48 and 49 are of l0-liter capacity.

For further protection, adjacent the hopper section and at the base of the filtering bags (not shown) eleventh and twelth explosion extinguishers are located above the floor grading so as to release their agent into the respective collector 20 and 21. In practice it is preferred that these be of approximately 30-liter capacity. These extinguishers 50 and 51 may also be used to provide fire suppression and advance inerting in the bag house portion of the collectors 20 and 21.

As earlier indicated the extinguishing agent used in these twelve extinguishers 40 through 51 may be bromochloromethane or equivalent substance. The mechanism by which these agents act to arrest combustion may be one of chemical inhibition. Inasmuch as combustion seems to be a chemical reaction, it is dependent upon certain radicals in the pre-flame zone to branch these chains, thereby substaining an advancing flame front. The halogenated hydrocarbons, such as bromochloromethane and bromotrifluoromethane, react with these radicals, thereby terminating the chains.

As also earlier indicated, it will be understood by those skilled in the art that the eight sensors or explosion detectors 32 through 39 will be operatively connected with various of the twelve high-rate discharge explosion extinguishers 40 through 51 so as to protect those parts of the system to which they are applied. All

of these sensors are also operatively connected to the various means for actuating the coal preparation system so that upon actuation of any one of the sensors the system itself will be completely shut down. The details of these last described arrangements are not illustrated in detail but are included in the schematic depiction represented by the drawing as described above.

The particular placements of the eight sensors 32 through 39, and of the twelve extinguishers 40 through 51, are critical to the successful functioning of this'particular system for the safe handling of pulverized coal and this constitutes the heart of the invention.

Protection against fire, as distinguished from explosion, may also be incorporated into this system. As earlier indicated a practical way of achieving this is to make use of the known Cardox detectors and extinguishers by means of which carbon dioxide may be directed into those parts of the system which are particularly sensitive to the hazards of fire. To this end, a first sensor 61 is located in connection with the pulverizer or mill 12. A second sensor 62 is associated with the cyclone 16 via its outlet duct 19. Third and fourth sensors 63 and 64 are provided in association with the filters 20 and 21. These four sensors 61 through 64 protect the main parts of the coal handling system from fire via, of course, the extinguishers to which they are operatively connected. As earlier indicated, it is to the protection of this part of the coal preparation system that the explosion suppression system is primarily directed. With respect to fire, however, it has been found desirable to incorporate additional sensors and extinguishers in those parts of the auxiliary systems which are connected to the coal preparation system via the coal storage tank 17. To this end, fifth and sixth sensors 65 and 66 are provided towards the top and discharge ends of the coal storage tank 17 and are arranged to be sensitive to fire not only in such tank but also in the auxiliary systems represented by the reference numerals 26, 27 and 31.

The fire extinguishers for protecting the system may be located in the following manner. Three are shown as being associated with the pulverizer 12 as indicated at 71, 72 and 73. A fourth extinguisher is associated with the cyclone 16 as indicated at 74. Four more extinguishers 75, 76, 77 and 78 are located within the bag house filters 20 and 21 as indicated. Ninth, tenth and eleventh extinguishers 79, 80 and 81 may be associated with the coal storage tank 17 while the final three extinguishers 82, 83 and 84 may be associated with the auxiliary systems designated by the reference numerals 26, 27 and 31.

It will be understood by those skilled in the art that the six sensors 61 through 66 are operatively connected with the 14 extinguishers 71 through 84 in conventional manner. The details of these connections, therefore, are again only schematically illustrated in the drawing and accompanying description. The actual operation of these devices is not the point of novelty herein but rather it is their specific location in the coal preparation system that is of importance. It will be further understood that the six sensors 61 through 66 are also tied into the means which actuate the coal preparation system so that upon actuation of any one of the sensors the complete system will be shut down.

By way of further description it is noted that pulverized coal discharged from the mill 12 may be in the neighborhood of 155F while the heated air in the bag filters 20 and 21 may be in the neighborhood of 1 10 to F. These temperatures are needed to insure the removal of surface moisture from the coal particles. It is also these temperatures, therefore, which render the system subject to explosion and fire and, of course, the invention is directed to suppressing such events before they really get started. A typical coal preparation system may operate on 10 to 16 tons per hour and the temperature blown into the pulverizer 12 will depend on ambient air temperture, the moisture of the coal and the amount of coal. When large quantities of relavely moist coal are employed, hotter air must be forced into the pulverizing unit.

In the coal preparation system, air (containing oxygen, naturally) is used as the carrier and this increases the probabilities of explosion and/or fire. A fuel (the coal), plus oxygen (in the carrier), plus ignition means (relatively high temperature) create the problem. Ignition may also be caused by tramp metal in the coal rubbing against metal ducts and the like whereby to cause sparking. Preferably, therefore, magnets may be located in certain areas to trap such magnetic tramp metal before it enters the coal preparation system; by way of illustration, one such magnet is schematically depicted at 90.

In prior coal preparation systems wherein pulverized coal was fed directly into a blast furnace and the like without interruption, the dangers of explosion and/or fire were not so great. Introduction of bag filters and the like, however, slows down the operation and increases the dangers. By the same token, it appears that because movement of pulverized coal from the pulverizer to the cyclone separator is relatively fast, the dangers, although real, are not so pronounced as when the velocity becomes slower, as from the separator through the filters to the storage tank.

In setting the explosion sensors, the normal pressure level in the coal preparation system if first determined. The eight sensors 32 through 39 are then set to be sensitive to a pressure slightly higher then the normal operating process pressure. When such higher pressures are sensed, the explosion extinguishers are actuated.

Similarly, the normal operating temperature of the coal preparation system is determined and the six sensors 61 through 66 are set so as to be sensitive to temperatures slightly above process temperatures whereupon the fire extinguishers will be actuated to shoot, for example, carbon dioxide into the system. In the preferred arrangement these fire extinguishers will operate to eliminate a source of ignition thereby preventing an explosion as well as to suppress fire, and in such arrangement actuation of the fire sensors and extinguishers may deactivate the explosion suppression system so as to render unnecessary reloading of such latter system; in any event, the operator may do this manually if circumstances warrant it.

Manually operated fire extinguishers may be located throughout the system as desired. Three such of these have been indicated at 91, 92 and 93 in association with the coal bunker 10, the storage tank 17, and the auxiliary systems 26, 27, 31. Even when a substantially inert gas such as CO plus nitrogen is employed, such as in the storage tank and auxiliary systems, there may be some oxygen present. If this gas is kept relatively low in oxygen content, about one-half percent, dangers are minimal; but as the oxygen content passes 6 to 8 percent, dangers become magnified. These additional Cardox extinguishers 91-93, therefore, provide an extra measure of safety.

It is believed that the foregoing constitutes a full and complete description of the invention. It will be apparent to those skilled in the art that modification may be made in the system without departing from the scope and spirit thereof. And while the system has been schematically depicted and described in terms of certain particular structures and arrangements, these are not to consitute a limitation on the invention except insofar as they are specifically set forth in the subjoined claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A system for the safe handling of pulverized coal including: loading means for feeding raw coal into the system; pulverizing means to grind and heat lump coal received from the loading means to a dry powder condition; separator means to divide out the fines; a coal powder storage tank; filter means; first duct means connecting the pulverizing means to the separator means; second duct means connecting the separator means directly to the storage tank; third duct means connecting the separator means to the filter means; fourth duct means connecting the filter means to the storage tank; a plurality of explosion detectors; a plurality of explosion extinguishers; means interconnecting said explosion detectors and said explosion extinguishers so that when pressures above normal operating pressures develop said explosion extinguishers will be actuated; a said explosion detector in close association with said pulverizing means and a said explosion extinguisher for discharging explosion suppression agent into said pulverizing means; a said explosion detector in close association with said separator means and a said explosion extinguisher for discharging explosion suppression agent into said separator means; a said explosion detector in close association with said filter means and a said explosion extinguisher for discharging explosion suppression agent into said filter means; and means interconnecting said explosion detectors with said loading means, said pulverizing means and said separator means so that when said explosion extinguishers are actuated said loading means, said pulverizing means and said separator means are simultaneously inactivated whereby to shut down the system.

2. The system of claim 1 including a plurality of fire detectors; a plurality of fire extinguishers; means interconnecting said fire detectors and said fire extinguishers so that when temperatures above normal operating temperatures develop said fire extinguishers will be actuated; and means interconnecting said fire detectors with said loading means, said pulverizing means and said separator means so that when said fire extinguishers are actuated said loading means, said pulverizing means and said separator means are simultaneously inactivated whereby to shut down the system.

3. The system of claim 1 in which there are two of said filter means and a branch duct from said third duct means to a filter means so that both of said filter means receive coal powder from said separator means, there being an explosion detector and an explosion extinguisher for each of said filter means.

4. The system of claim 3 in which said separator means is a cyclone separator and said filter means is a pair of bag filters.

5. The system of claim 4 including an additional explosion extinguisher for said cyclone separator, one said explosion extinguisher being located in said third duct means and being directed towards said separator, the other of said explosion extinguishers being located in said cyclone separaton 6. The system of claim 4 including two additional explosion extinguishers for each of said bag filters whereby there are three said explosion extinguishers for each said filter, two of said three explosion extinguishers being located in each of said bag filters and the other of said three explosion extinguishers being located in the said duct means extending from said cyclone separator to each said bag filter and being directed to a respective said bag filter.

7. A system for the safe handling of pulverized coal including; loading means for feeding raw coal into the system; pulverizing means to grind and heat lump coal received from the loading means to a dry powder condition; separator means to divide out the fines; a coal powder storage tank; filter means; first duct means connecting the pulverizing means to the separator means; second duct means connecting the separator means directly to the storage tank; third duct means connecting the separator means to the filter means; fourth duct means connecting the filter means to the storage tank; a plurality of explosion detectors; a plurality of explosion extinguishers; means interconnecting said explosion detectors and said explosion extinguishers so that when pressures above normal operating pressures develop said explosion extinguishers will be actuated; said separator means comprising a cyclone separator; said filter means comprising a pair of bag filter; said third duct means comprising two branch ducts, each of said branch ducts extending from said cyclone separator to respective ones of said bag filters; there being eight of said explosion detectors located as follows; one closely adjacent said pulverizing means; two in the said first duct means, one towards the pulverizing means and the other near the said cyclone separator; one in the said third duct means near the said cyclone separator; one in each of said two branch ducts; and one in each of said two bag filters; there being twelve of said explosion extinguishers located as follows: one adjacent said pulverizing means directed toward said pulverizing means; three in said first duct means directed towards said pulverizing means; one in said third duct means directed towards said cyclone separator; one in said cyclone separator; one in each of said two branch ducts directed towards said bag filters; and two in each of said bagfilters; and means interconnecting said explosion detectors with said loading means, said pulverizing means and said separator means so that when said pulverizing means and said separator means so that when said explosion extinguishers are actuated said loading means, said pulverizing means and said separator means are simultaneously inactivated whereby to shut down the system.

8. A system for the safe handling of pulverized coal including: loading means for feeding raw coal into the system; pulverizing means to grind and heat lump coal received from the loading means to a dry powder condition; separator means to divide out the fines; a coal powder storage tank; filter means; first duct means connecting the pulverizing means to the separator means; second duct means connecting the separator means directly to the storage tank; third duct means connecting the separator means to the filter means; fourth duct means connecting the filter means to the storage tank;

means interconnecting said fire detectors and said fire extinguishers so that when temperatures above normal operating temperatures develop said fire extinguishers will be actuated; and means, said pulverizing means and said separator means so that when said fire extinguishers are actuated said loading means, said pulverizing means and said separator means are simultaneously inactivated whereby to shut down the system.

9. The system of claim 8 including additional means interconnecting said fire detectors with said explosion detectors so that actuation of the said fire detectors and the said fire extinguishers will deactivate the said explosion detectors whereby the said explosion extinguishers are inactivated, so as to render unnecessary the reloading of the explosion extinguishers when the situation has been taken care of by actuation of the fire extinguishers.

UNITED STATES PATENT OFFICE Patent No. 3,912.015 Dated October 1, 1975 Inventor) ALLEN GARBEE, ET AL.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, Line 2 1, "of" should be --is- Column 3, Line 2, "ia" should be --has-- Column 4 Line ll, "21 should be --A-- Column 1, Line 16, "extinguisher" should be ----extinp;uishers-- Q Column 4 Line 251 "ty icallv" should he --Tynicallv-- Column 6, Line 4 4, if" should he ---is-- Column 8, Line 58 throu h 61, the phrase nulverizing means and said seoarator means so that when said should be deleted. Column 9, Line 19 free" should he --fire- Column 10, Line 4, after "means (first occurance) there should be inserted the phrase --interconnectine. said fire detectors with said loading means-- Signed and Scaled this seventeenth Day Of February 1976 [SEAL] Attest:

RUTH C. MASON C.MARSHALL DANN Atlesting Offic Commissioner oj'Parents and Trademarks 

1. A SYSTEM FOR THE SAFE HANDLING OF PULVERIZED COAL INCLUDUNG LOADING MEANS FOR FEEDING RAW COAL INTO THE SYSTEM, PULVERIZING MEANS TO GRIND AND HEAT LUMP COAL RECEIVED FROM THE LOADING MEANS TO A DRY POWDER CONDITION, SEPERATOR MEANS TO DIVIDE OUT THE FINES, A COAL POWDER STORAGE TANK, FILTER MEANS, FIRST DUCT MEANS CONNECTING THE PULVERIZING MEANS TO THE SEPERATOR MEANS, SECOND DUCT MEANS CONNECTING THE SEPERATOR MEANS DIRECTLY TO THE FILTER MEANS, FOURTH DUCT MEANS ING THE SEPARATOR MEANS T THE FILTER MEANS, FOURTH DUCT MEANS CONNECTING THE FILTER MEANS TO THE STORAGE TANK, A PLURALITY OF EXPLOSION DETECTORS, A PLURALITY OF EXPLOSION EXTINGUISHERS, MEANS INTERCONNECTING SAID EXPLOSION DETECTORS AND SAID EXPLOSION EXTINGUISHERS SO THAT WHEN PRESSURES ABOVE NORMAL OPERATING PRESSURES DEVELOP SAID EXPLOSION EXTINGUISHER WILL BE ACTUATED, A SAID EXPLOSION DETECTOR IN CLOSE ASSOCIATION WITH SAID PULVERIZING MEANS AND A SAID EXPLOSION EXTINGUISHER FOR DISCHARGEING EXPLOSION SUPPRESSION AGENT INTO SAID PULVERIZING MEANS, A SAID EXPLOSION DETECTOR IN CLOSE ASSOCIATION WITH SAID SEPERATOR MEANS AND A SAID EXPLOSION EXTINGUISHER FOR DISCHARGING EXPLOSION SUPPRESSION AGENT INTO SAID SEPARATOR MEANS, A SAID EXPLOSION DETECTOR IN CLOSE ASSOCIATION WITH SAID FILTER MEANS AND A SAID EXPLOSION EXTINGUISHER FOR DISCHARGING EXPLOSION SUPPRESSION AGENT INTO SAID FILTER MEANS, AND MEANS INTERCONNECTING SAID EXPLOSION DETECTORS WITH SAID LOADING MEANS, SAID PULVERIZING MEANS AND SAID SEPERATOR MEANS AO THAT WHEN SAID EXPLOSION EXTINGUISHEERS ARE ACTUATED SAID LOADING MEANS, SAID PULVERIZING MEANS AND SAID SEPERATOR MEANS ARE SIMULTANEOUSLY INACTIVATED WHEREBY TO SHUT DOWN THE SYSTEM.
 2. The system of claim 1 including a plurality of fire detectors; a plurality of fire extinguishers; means interconnecting said fire detectors and said fire extinguishers so that when temperatures above normal operating temperatures develop said fire extinguishers will be actuated; and means interconnecting said fire detectors with said loading means, said pulverizing means and said separator means so that when said fire extinguishers are actuated said loading means, said pulverizing means and said separator means are simultaneously inactivated whereby to shut down the system.
 3. The system of claim 1 in which there are two of said filter means and a branch duct from said third duct means to a filter means so that both of said filter means receive coal powder from said separator means, there being an explosion detector and an explosion extinguisher for each of said filter means.
 4. The system of claim 3 in which said separator means is a cyclone separator and said filter means is a pair of bag filters.
 5. The system of claim 4 including an additional explosion extinguisher for said cyclone separator, one said explosion extinguisher being located in said third duct means and being directed towards said separator, the other of said explosion extinguishers being located in said cyclone separator.
 6. The system of claim 4 including two additional explosion extinguishers for each of said bag filters whereby there are three said explosion extinguishers for each said filter, two of said three explosion extinguishers being located in each of said bag filters and the other of said three explosion extinguishers being located in the said duct means extending from said cyclone separator to each said bag filter and being directed to a respective said bag filter.
 7. A system for the safe handling of pulverized coal including; Loading means for feeding raw coal into the system; pulverizing means to grind and heat lump coal received from the loading means to a dry powder condition; separator means to divide out the fines; a coal powder storage tank; filter means; first duct means connecting the pulverizing means to the separator means; second duct means connecting the separator means directly to the storage tank; third duct means connecting the separator means to the filter means; fourth duct means connecting the filter means to the storage tank; a plurality of explosion detectors; a plurality of explosion extinguishers; means interconnecting said explosion detectors and said explosion extinguishers so that when pressures above normal operating pressures develop said explosion extinguishers will be actuated; said separator means comprising a cylone separator; said filter means comprising a pair of bag filter; said third duct means comprising two branch ducts, each of said branch ducts extending from said cylone separator to respective ones of said bag filters; there being eight of said explosion detectors located as follows; one closely adjacent said pulverizing means; two in the said first duct means, one towards the pulverizing means and the other near the said cyclone separator; one in the said third duct means near the said cyclone separator; one in each of said two branch ducts; and one in each of said two bag filters; there being twelve of said explosion extinguishers located as follows: one adjacent said pulverizing means directed toward said pulverizing means; three in said first duct means directed towards said pulverizing means; one in said third duct means directed towards said cyclone separator; one in said cyclone separator; one in each of said two branch ducts directed towards said bag filters; and two in each of said bag filters; and means interconnecting said explosion detectors with said loading means, said pulverizing means and said separator means so that when said pulverizing means and said separator means so that when said explosion extinguishers are actuated said loading means, said pulverizing means and said separator means are simultaneously inactivated whereby to shut down the system.
 8. A system for the safe handling of pulverized coal including: loading means for feeding raw coal into the system; pulverizing means to grind and heat lump coal received from the loading means to a dry powder condition; separator means to divide out the fines; a coal powder storage tank; filter means; first duct means connecting the pulverizing means to the separator means; second duct means connecting the separator means directly to the storage tank; third duct means connecting the separator means to the filter means; fourth duct means connecting the filter means to the storage tank; a plurality of explosion detectors; a plurality of explosion extinguishers; means interconnecting said explosion detectors and said explosion extinguishers so that when pressures above normal operating pressures develop said explosion extinguishers will be actuated; means interconnecting said explosion detectors with said loading means, said pulverizing means and said separator means so that when said explosion extinguishers are actuated said loading means, said pulverizing means and said separator means are simultaneously inactivated whereby to shut down the system; a plurality of free detectors; a plurality of fire extinguishers; means interconnecting said fire detectors and said fire extinguishers so that when temperatures above normal operating temperatures develop said fire extinguishers will be actuated; and means, said pulverizing means and said separator means so that when said fire extinguishers are actuated said loading means, said pulverizing means and said separator means are simultaneously inactivated whereby to shut down the system.
 9. The system of claim 8 including additional means interconnecting said fire detectors with said explosion detectors so that actuation of the said fire detectors and thE said fire extinguishers will deactivate the said explosion detectors whereby the said explosion extinguishers are inactivated, so as to render unnecessary the reloading of the explosion extinguishers when the situation has been taken care of by actuation of the fire extinguishers. 